Multimodal dynamic robotic systems

ABSTRACT

Robotic systems include a frame or body with two or more wheels rotatably mounted on the frame or body and a motor for driving each wheel. A system controller generates a signal for actuating each motor based on information provided by one or more sensors in communication with the system controller for generating feedback signals for providing reactive actuation of the motors for generating one or more functions selected from the group consisting of forward motion, backward motion, hopping, climbing, and balancing. A power source is included for providing power to operate the drive motors, system controller and the one or more sensors.

RELATED APPLICATIONS

This application is continuation of application Ser. No. 14/656,676,filed Mar. 12, 2015, issued as U.S. Pat. No. 9,757,855, which is adivisional of application Ser. No. 13/389,256, filed Mar. 15, 2012,issued as U.S. Pat. No. 9,020,639, which is a 371 national stage filingof International Application No. PCT/US2010/044790, filed Aug. 6, 2010,which claims the priority of U.S. Provisional Applications No.61/231,672, filed Aug. 6, 2009, and No. 61/324,258, filed Apr. 14, 2010.Each of the foregoing applications is incorporated herein by referencein its entirety.

FIELD OF THE INVENTION

The present invention relates to robotic mechanisms that exhibitmultimodal capability including rolling, hopping, balancing, climbing,and picking up and throwing objects. More particularly, the inventionrelates to multimodal dynamic robotic systems that can move and functionefficiently on complex terrain and/or in harsh operating environments.

BACKGROUND OF THE INVENTION

Robots have been developed for applications ranging from materialtransportation in factory environments to space exploration. One area inwhich mobile robots have been widely adopted is in the automobileindustry, where robots transport components from manufacturing workstations to the assembly lines. These automated guided vehicles (AGVs)follow a track on the ground and have the ability to avoid collisionswith obstacles in their path. Autonomous mobile robots designed forplanetary exploration and sample collection during space missions, suchas NASA's Mars Exploration Rover, have also received significantattention in recent years. This attention has resulted in advancement ofmobile robot technology and a corresponding increase in theeffectiveness of mobile robots in a wide range of applications.

Mobile robot technology has primarily focused on robot designs having abody with wheels for mobility. This has led to advancements in motionplanning and control of the rolling wheel. Notwithstanding thesedevelopments, wheeled mobile robots have significant deficiencies thathave not been adequately overcome. For example, wheeled robotsfrequently have difficulty traversing rough terrain. While this problemmay be reduced by increasing the size of the wheels of the robot,increases in wheel size cause various undesirable consequences includingan increase in the overall size and weight of the robot. Further,increases in wheel sizes do not necessarily result in correspondingincreases in operational features such as payload capacity. Also,wheeled robots can be adversely affected by harsh operating environmentssuch as heat, chemicals, and the like.

A variation of a wheeled robot that addresses certain difficulties foundin harsh environments is described in U.S. Patent Publication No.2008/0230285 A1, which shares partial inventorship with the presentapplication. The cited application, which is incorporated herein byreference, describes the first vehicle of its kind that combinesefficient wheeled locomotion with a hopping capability. The multimodalrobot adds hopping and climbing capability to a wheeled robot byattaching the axle to a central leg so that relative movement of the legand axle can lift axle. A hopping action can be produced by applyingsudden downward force to drive the leg against the support surface.Stair climbing is provided by applying a steady force against thesupport surface to allow the wheels to climb up the vertical riser. Theleg also provides additional stabilization for movement across uneventerrain. In one embodiment, the multimodal robot's wheels are mounted onindependently-moving axes that have independent parallelogram linkagesto permit the wheels to change relative orientations and tilt.

One alternative to the wheeled robot is the rolling robot. A rollingrobot is one that rolls on its entire outer surface rather than onexternal wheels or treads. They tend to be spherical or cylindrical inform and have a single axle, if any axle at all, and an outer surfacethat is fully involved in the robot's movement. State-of-the-art rollingrobots are all based on the principle of moving the center of gravity ofa wheel or sphere, which causes the wheel or sphere to fall in thedirection of movement and thus roll along. Rolling robots have a numberof advantages over wheeled robots including that the components of therobot are enclosed within a shell, so there are no extremities tohang-up on obstacles, they don't fall over, they can travel on softsurfaces, including water, and they can move in any direction and turnin place.

Improvements in methods of locomotion are needed to allow roboticsystems to move within environments that are difficult or impossible forcurrently-used robot locomotion designs to traverse. The followingdescription discloses such improvements.

BRIEF SUMMARY

It is an advantage of the present invention to provide a multimodalrobot that can move and function efficiently on complex terrain and/orin harsh operating environments.

In an exemplary embodiment, the robotic systems according to theinvention include a frame or body with two or more wheels rotatablymounted on the frame or body and a motor for independently driving eachwheel. A system controller generates a signal for actuating each motorbased on information provided by one or more sensors in communicationwith the system controller for generating feedback signals for providingreactive actuation of the motors for generating one or more functionsselected from the group consisting of forward motion, backward motion,climbing, hopping, balancing, and throwing. A power source is includedfor providing power to operate the drive motors, system controller andthe one or more sensors.

In one aspect of the invention, a robotic system according includes aframe with two or more wheels rotatably mounted thereon and a motor forindependently driving each wheel. A system controller generates a signalfor actuating each motor based on information provided by one or moresensors in communication with the system controller for generatingfeedback signals for providing reactive actuation of the motors forgenerating one or more functions selected from the group consisting offorward motion, backward motion, climbing, hopping, balancing, andthrowing. A power source is included for providing power to operate thedrive motors, system controller and the one or more sensors. The frameincludes two arms, each having a distal end on which a wheel is mountedand a proximal end and a leg centrally disposed between the two armswith the proximal end of each arm rotatably attached to the leg. An armmotor is disposed on each arm for independently driving rotation of thearm relative to the leg, so that when the leg is disposed in a verticalorientation with an end of the leg in contact with a support surface,(i) downward symmetrical rotation of the arms positions the wheels incontact with the support surface for wheeled locomotion on the supportsurface, (ii) rapid upward symmetrical rotation of the arms lifts theleg off of the support surface to produce a hopping motion; and (iii)antisymmetrical rotation of the arms balances the frame on the end ofthe leg. In another aspect of the invention, a robotic system accordingincludes a body with two or more wheels rotatably mounted thereon and amotor for independently driving each wheel. A system controllergenerates a signal for actuating each motor based on informationprovided by one or more sensors in communication with the systemcontroller for generating feedback signals for providing reactiveactuation of the motors for generating one or more functions selectedfrom the group consisting of forward motion, backward motion, climbing,hopping, balancing, and throwing. A power source is included forproviding power to operate the drive motors, system controller and theone or more sensors. The body comprises a chassis having two drivewheels rotatably mounted on opposite sides thereof, each drive wheeldisposed on an axle that is rotated by a corresponding drive motor forrotating the drive wheel. A pair of elongated arms is rotatably mountedon opposite sides of and perpendicular to the chassis, each arm having aproximal end disposed on a corresponding axle, and a distal end, onwhich a second wheel is mounted in a common plane with the correspondingdrive wheel. A second motor is associated with each arm, and a linkagebetween the second motor and the axle for each arm causes the secondmotor, when activated, to rotate one of the chassis and thecorresponding arm relative to the other. Independent activation of thesecond motor of both arms to rotate the arms symmetrically relative tothe chassis shifts a center of gravity for balancing on one of thedistal end or proximal end of the arms. The linkage between the secondmotor and the axle for each arm and a linkage between the drive motorand the drive wheel can be incorporated into a two-degree of freedomjoint. In one embodiment, each arm supports a track.

In still another aspect of the invention, a robotic system accordingincludes a body with two or more wheels rotatably mounted thereon and amotor for independently driving each wheel. A system controllergenerates a signal for actuating each motor based on informationprovided by one or more sensors in communication with the systemcontroller for generating feedback signals for providing reactiveactuation of the motors for generating one or more functions selectedfrom the group consisting of forward motion, backward motion, climbing,hopping, balancing, and throwing. A power source is included forproviding power to operate the drive motors, system controller and theone or more sensors. The body comprises a chassis having two drivewheels rotatably mounted on opposite sides thereof, attached to acorresponding drive motor for rotating the drive wheel. A pair ofelongated drive arms is rotatably mounted on opposite sides of andperpendicular to the chassis, with each drive arm having a proximal enddisposed on a corresponding axle, and a distal end which supports asecond wheel in a common plane with the corresponding drive wheel. Aboom arm comprising a weighted portion attached to connector arms thatare pivotably mounted on each side of the chassis so that the weightedportion is disposed parallel to the chassis. At least one second motoris connected to the connector arms by a linkage such that activation ofthe at least one second motor rotates one of the chassis and the boomarm relative to the other. Independent activation of the at least onesecond motor shifts a center of gravity for balancing on one of thedistal end or proximal end of the drive arms. The system controllercontrols the drive motors and the at least one second motor toreactively shift the center of gravity for stability. In one embodiment,each arm supports a track.

In another aspect of the invention, a robotic system according includesa frame with two or more wheels rotatably mounted thereon and a motorfor independently driving each wheel. A system controller generates asignal for actuating each motor based on information provided by one ormore sensors in communication with the system controller for generatingfeedback signals for providing reactive actuation of the motors forgenerating one or more functions selected from the group consisting offorward motion, backward motion, climbing, hopping, balancing, andthrowing. A power source is included for providing power to operate thedrive motors, system controller and the one or more sensors. The two ormore wheels comprise a plurality of reaction wheels and the motor fordriving each reaction wheel is disposed within a housing to define aplurality of momentum exchange elements mounted on one or more axesattached to the frame. The frame comprises a geometrical structure whichallows the plurality of momentum exchange elements to be distributedabout the frame to individually or simultaneously generate angularmomentum in a plurality of different directions. In one variation, theone or more axes comprise a single gimbal axis, each having acorresponding gimbal motor. In another variation, the one or more axescomprise a double gimbal axis, each having two corresponding gimbalmotors. A shell may be provided to enclose the frame and momentumexchange elements.

In yet another aspect of the invention, a robotic system includes a bodywith two or more wheels rotatably mounted thereon and a motor forindependently driving each wheel. A system controller generates a signalfor actuating each motor based on information provided by one or moresensors in communication with the system controller for generatingfeedback signals for providing reactive actuation of the motors forgenerating one or more functions selected from the group consisting offorward motion, backward motion, climbing, hopping, balancing, andthrowing. A power source is included for providing power to operate thedrive motors, system controller and the one or more sensors. The body isconfigured as a cylinder having a rotational axis, the cylinder havingtwo ends, each end defining a hub having an axle aligned with therotational axis for rotatably retaining a wheel, the body having acavity therein defining a storage volume for retaining an object havingan object diameter. An elongated arm extends away from the bodyperpendicular to the rotational axis so that a base portion of theelongated arm is in communication with the storage volume. A lower bodyportion opposite the elongated arm is symmetrical along a planebisecting the cylinder. A curved channel is located on each side of thebisecting plane with an exit end in communication with the storagevolume and an entrance end defined by the hub, the lower body portionand an inner surface of the wheel. Each channel has a dimension forreceiving the object to produce a frictional contact between the innersurface of the wheel, the hub and the lower body portion, so thatrotation of the wheel draws the object into the channel and into thestorage volume. The drive motors are adapted for rotating the bodyrelative to the wheels so that the elongated arm can be oriented in ahorizontal position. With the elongated arm oriented in a horizontalposition, rapid activation of the motors rotates the correspondingwheels in a first direction causing the body to rotate around therotational axis in an opposite direction to rapidly accelerate thehorizontal arm toward a vertical position. An object disposed on thebase portion of the elongated arm rolls toward a distal end of the armas the elongated arm accelerates toward the vertical position, causingthe object to be thrown when the object reaches the distal end of thearm.

In a first exemplary embodiment, enhanced mobility within a harshenvironment, which may include rough terrain or hazards, is provided ina modification of a wheeled robot which combines a hopping ability witha leaning maneuver. The inventive robot includes end-over-end stairclimbing capability, which involves raising its center of mass above theobstacle while balancing the vehicle on its toe and shifting the mass ofthe drive wheels side-to side for balance.

The robot of the first embodiment comprises two independently drivenwheels mounted on the ends of two independently driven arm assemblieswhich pivot about a central leg to produce both symmetric andanti-symmetric rotation, depending on the motion desired. The armassemblies are adapted to linearly travel along the length of the legvia a non-backdriveable motorized lead screw. This gradual linear motionallows the vehicle to transition between an upright roving configurationand a toe-balancing configuration.

The independently-actuated arms can function both as a hopping mechanismwhen rotated symmetrically about the central leg, and as anactively-controlled roll-axis stabilizer when rotated anti-symmetricallyrelative to the central leg. Appropriate superposition of these twomotions allows the robot to simultaneously stabilize and hop in the rollaxis plane.

The multimodal robot of the present invention improves upon previousdesigns by leveraging a highly-efficient leaning maneuver whileretaining the hopping capabilities necessary to overcome otherobstacles, including jumping onto a raised platform or across a gap, orquickly traversing flames or other hazards that could damage aslower-moving robot.

Applications for the multimodal robot of the first embodiment includereconnaissance in burning or chemical-contaminated environments,monitoring hazardous materials (e.g. nuclear waste stockpiles),providing mobile platforms for weapons, planetary exploration, and forincorporation in toys.

A second embodiment of a multimodal robot combines rolling, balancingand climbing capabilities in a wheeled or treaded vehicle by changingthe vehicle's center of gravity relative to its chassis. These multiplemodes of operation allow the vehicle to perform and stabilize “wheelies”and “reverse wheelies” (also known as “stoppies”). In an exemplaryembodiment, the robot is capable of overcoming obstacles nearly as tallas the vehicle is long (in its folded configuration) by reconfiguringitself to adjust its center of gravity. A platform or frame ispreferably connected to the chassis to carry a payload, sensors, camerasor other electronic devices. In a preferred configuration, motors thatdrive the treads or wheels are capable of independent rotation withrespect to the chassis, so that the treads or wheels may be used in boththe rolling and balancing functions. This allows the robot todynamically adjust its center of gravity. MEMS accelerometers andgyroscopes, coupled with advanced filtering techniques, allow the robotto estimate its angle with respect to gravity. With the tread assembliesunfolded away from the body, the robot can balance upright on itstreaded “toes” and stand up in order to expand the view of an onboardcamera (or other sensors) and overcome obstacles that would otherwise beinsurmountable with a treaded robot that is of the same height as therobot in its conventional treaded mode. This design is also capable ofboth crossing chasms nearly as wide as the vehicle is long, and usingthe front-mounted pivot of the chassis to actively dampen vibrationswhen driving quickly over rough terrain. The reconfigurability of thetread assemblies permits several modes of locomotion, which can beselected to adapt the robot to the type of terrain encountered. Theunique mechanical design of this multimodal robot coupled with feedbackcontrol algorithms enables it to overcome complex terrain (e.g. stairs,rubble) while retaining a small form factor to navigate in confinedspaces and to reduce cost and weight.

In an alternative configuration, an actuated boom is included tofacilitate balancing and climbing. The boom has significant mass,approximately equal to the mass of the chassis. Motors are configured onthe robot to drive the treads (or wheels) and to change the angle of theboom with respect to the chassis. Sensors are integrated to detect therobot's configuration, including one or more level sensors along eachaxis, which provide signals to a system controller. Feedback may beapplied to enable the vehicle to balance on its front or rear treadedtoes (or wheels). The vehicle can also climb obstacles (includingstairs) by extending the mass of the boom over the obstacle and rotatingthe chassis up and over. This maneuver may be done in a staticallystable manner or in a dynamically balanced manner. The boom arm may beextensible and/or may be configured with its own wheels or treads, Theshifting of the robot's center of gravity allows it to overcomeobstacles nearly as tall as the vehicle is long (in its foldedconfiguration) by repositioning its boom arm.

Applications of this multimodal robot include building, cave, and mineexploration; search and rescue; monitoring hazardous materials (e.g.nuclear waste stockpiles); improvised explosive device (IED) detectionand disposal; weapons platform; toy; planetary exploration; HVAC systemmonitoring.

In a third embodiment, motion in harsh operating environments and uneventerrain is provided by a spherical robot that incorporates momentumexchange devices to achieve rapid acceleration or deceleration in anydirection.

The inventive spherical robot can efficiently traverse a wide variety ofterrain including, but not limited to: carpet, pavement, sand, gravel,and mud. In addition, it can incorporate an amphibious capability whichallows it to traverse mud, swamp, and open water. Unlike existingspherical robots, the internal frame of the present embodiment is fixedto the external sphere and the center of mass of the robot remains fixedto the center of the sphere. In an exemplary embodiment, single-gimbaledcontrol moment gyroscopes (CMGs) are used for momentum exchange. Thisdesign is especially agile, as the momentum needed to maneuver is storedwithin the CMGs and, thus, does not need to be generated by high-torque(and large electrical power-consuming) motors like a standard directdrive system.

In one embodiment, a cubical frame is populated with four single-gimbalCMGs, with each gimbal axis at an angle on each face. A plurality ofother momentum exchange devices such as reaction wheels, dual-gimbalCMGs, or momentum wheels may be incorporated as alternatives to thesingle-gimbal CMGs. The robot is not limited to spheres as an outerstructure, but to all generalized amorphous ellipsoidal configurationsas well.

In military applications, the inventive spherical robot can be used incovert reconnaissance or munitions delivery. For the general commercialapplications, the robots can be a toy or a therapeutic device.

The fourth embodiment of the multimodal robot is a wirelessly-controlledor autonomous vehicle which is an all-in-one system of ball retrieval,storage and throwing. The design includes an integrated ball pick upmechanism and the jai alai style throwing arm design.

To enable ball pick up, the body and wheels of the robot are spaced toprovide automatic pickup and loading of the target balls. This methodallows the operator to drive the robot toward the target, with thecurvature of the robot directing the ball into the space between thewheel and the body. The rotation of the wheel brings the ball up to bestored within a basket or other storage receptacle.

For throwing, the robot is stabilized by a feedback control circuit tobalance upright as an inverted pendulum. The great rotational inertia ofthe wheels allows the robot to rotate the body quickly from a lay-downmode to an upright mode. The rapid rotation results in the effectivetoss of a light weight ball. The ball is imparted with a spin as itrolls off the throwing arm track. The result is a more stable and longerthrow.

The potential applications of the present robot embodiment includeremote controlled toy cars, an automatic tennis ball retrieval system,and a grenade launcher, among others.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a diagrammatic front view of a first embodiment of amultimodal robot; FIG 1b is a detail view of the circled area in FIG. 1a.

FIG. 2 is a diagrammatic perspective view of the hopping robot of FIG.1.

FIG. 3 is a diagrammatic perspective view of the arm assemblies of thehopping robot.

FIG. 4 is a series of cartoons illustrating the modes of operation ofthe robot of FIG. 1.

FIGS. 5a and 5b illustrate configuration of the arm assemblies duringmotion, where FIG. 5a shows a hopping motion; and FIG. 5b showsasymmetric arm motion for stabilization about the roll axis.

FIG. 6 is a diagrammatic front view of the multimodal hopping robot inan upright roving configuration.

FIG. 7 diagrammatically illustrates a self-locking arm suspensionmechanism.

FIG. 8 diagrammatically illustrates an alternative embodiment of the armsuspension mechanism.

FIG. 9 is a series of plots of effective spring resistance due tosymmetric rotation, showing angular displacement as a function of springstretch, resultant torque and effective torsional spring rate.

FIG. 10 is a series of plots of effective spring resistance due toantisymmetric rotation, showing angular displacement as a function ofspring stretch, resultant torque and effective torsional spring rate.

FIG. 11 is a plot of critical zero-torque arm angle (symmetric rotation)as a function of linkage parameters.

FIG. 12 is a perspective view of the arm mechanism of the first robotembodiment during conventional operation.

FIG. 13 is a perspective view of the first robot embodiment in ahorizontal roving configuration.

FIG. 14a is a diagrammatic perspective view of a multimodal robotaccording to a second embodiment; FIG. 14b is a diagrammatic side viewof an exemplary tread assembly.

FIGS. 15a-15c illustrate different modes of locomotion of the embodimentof FIG. 14, where FIG. 15a shows the robot in a heel-balancing position,FIG. 15b shows the robot in a toe-balancing position, and FIG. 15cshowing the robot with its treads extended for reaching across andspanning a gap, or for climbing. FIGS. 16a-16c illustrate an alternativeconfiguration of the multimodal robot of FIG. 14, in which an actuatedboom is used to shift the robot's center of gravity.

FIG. 17 illustrates an alternative configuration of the multimodal robotof FIG. 14 in which the treads are replaced with wheels.

FIG. 18 illustrates an alternative configuration of the multimodal robotof FIG. 16 a.

FIG. 19 is a diagrammatic view of the components of a hip joint of thesecond multimodal robot embodiment.

FIGS. 20a-20d are perspective views of the treaded robot, where FIG. 20ashows the robot in a horizontal skid steer configuration; FIG. 20b showsthe robot in a “chasm-crossing” configuration; FIG. 20c shows the robotin a vertical “C-balancing” configuration; and FIG. 20d shows the robotin a vertical “V-balancing” configuration.

FIGS. 21a and 21b illustrate examples of functions performed by themultimodal robot of FIG. 14, where FIG. 21a is a perspective view of therobot maneuvering within a duct, and FIG. 21b is a perspective view ofthe robot perching on the edge of a stair step.

FIG. 22a illustrates a sequence of steps in a climbing operationperformed by the robot of FIG. 14.

FIG. 22b diagrammatically illustrates actions executed by the robotcorresponding to the sequence of steps shown in FIG. 22 a.

FIG. 23 is a diagrammatic perspective view of a spherical robotaccording to the third multimodal robot embodiment.

FIGS. 24a-24c are diagrammatic views of three different prior artmomentum exchange devices that may be used in the spherical robot, whereFIG. 24a illustrates a reaction wheel assembly; FIG. 24b shows a singlegimbal control moment gyro; and FIG. 24c illustrates a double gimbalcontrol moment gyro.

FIG. 25 is shows four exemplary geometric configurations for a frame forsupporting the momentum exchange elements.

FIG. 26 is a three-dimensional computer drawing of a first exemplaryconstruction of the spherical robot.

FIG. 27a is a perspective drawing of a second exemplary construction ofthe spherical robot; FIG. 27b is an exploded view of the construction;FIG. 27c is an exploded view of one SGCMG element.

FIG. 28 is a block diagram showing the sequence of control operationsfor the spherical robot.

FIGS. 29a-29c illustrate examples of possible functions that can beperformed using the spherical robot, where FIGS. 29a and 29b showexamples of motion of the robot in a free-surface case and anear-a-surface case, respectively; and FIG. 29c is a series of cartoonsshowing the steps of a process for coordinating multiple sphericalrobots to overcome an obstacle.

FIG. 30 is a perspective view of a fourth multimodal robot embodiment.FIGS. 31a and 31b are a front view and a rear view, respectively, of thebody portion of the multimodal robot of FIG. 30.

FIGS. 32a and 32b are side views of the body portion with the wheelremoved showing steps in a sequence for picking up a round object.

FIG. 33 is a perspective view of latch for preventing the object fromrolling backward in the channel. FIGS. 34a and 34b are side andperspective views, respectively, of a ball release mechanism.

FIGS. 35a-35c are cross-sectional views of the robot body showing theball release sequence.

FIGS. 36a-36d are side views of the robot showing the throwing sequence,where FIG. 36a shows the ball at the lower portion of the throwing arm;FIG. 36b shows the beginning of the body rotation to move the ball to amid-point of the throwing arm; FIG. 36c shows the ball at the upperportion of the throwing arm; and FIG. 36d shows the ball after release.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following description of four embodiments of multimodal robotsprovide details of functions including locomotion via rotation of wheelsor tracks and spherical rotation, hopping, climbing, and throwing. Whilethe different embodiments may use different locomotion means, the commonfeature among all embodiments is their use of feedback to controlangular momentum to enable active balancing and effect changes inorientation and movement of the robots, resulting in vehicles that canbe used in a wide range of applications from military and industrialapplications to toys.

First Multimodal Robot Embodiment

Referring initially to FIGS. 1-3 and 6, the robot 10 of the firstembodiment (which may also be referred to herein as a “vehicle”)includes two independently driven wheels 6, 8 mounted on the ends of twoindependently driven arm assemblies 12, 14 that pivot about centralleg/shaft 16. The arm assemblies 12, 14 travel linearly along the lengthof leg 16 by way of a non-backdriveable motorized leadscrew 20. Thegradual motion provided by the screw 20 allows the vehicle 10 totransition between an upright roving configuration and a toe-balancingconfiguration (on toe 15 or 17 at the ends of leg 16). FIG. 2illustrates the three rotational axes around which the inventive robotmoves, with leg 16 corresponding to the yaw-axis, the axles of the drivewheels corresponding to the pitch-axis, and the arm carrier 21, to theextent that it defines the midpoint in the arm assembly, correspondingto the roll-axis.

Referring to FIG. 2, arm assemblies 12, 14 are linked to a central armcarrier 21 via joints 11 and 13, which extend through leg guide channels48 and 49. The arm carrier 21 is driven linearly along the leg 16 via aleadscrew powered by motors within the arm carrier to move joints 11 and13 along the lengths of the guide channels.

Left arm assembly 12 includes a parallelogram linkage, which has thebasic “frame” elements of a top left arm 22, bottom left arm 23, leftarm end link 30 and left arm mid-link 25. Similarly, right arm assembly14 includes the frame element of top right arm 18, bottom right arm 19,right arm mid-link 50 and right arm end link 47. The frame elements ofthe arms are preferably formed from a lightweight but relatively rigidmetal, such as aluminum or titanium. Alternatively, the frame elementsmay be formed from a strong, rigid plastic or other polymer. The jointsand drive mechanisms that connect and allow manipulation of the framebasic elements are described in more detail below.

The top left arm 22 attaches to the arm carrier 21 via joint 11, whichattaches to the left arm end-link 30 via joint 31. The bottom left arm23 is attached to left arm end-link 30 via joint 32 and to the armcarrier 21 via joint 13. The left arm mid-link 24 attaches to the topleft arm 22 via joint 4, and to the bottom left arm via joint 3. In allcases, the joints described herein are revolute joints.

The left spring lever 25 is attached to the left arm assembly via joints33 and 34. As illustrated, joint 34 is horizontally offset from themidpoint of a line connecting joints 31 and 32. The attachment betweenthe spring lever 25 and joint 34 consists of a standard revolute jointcoaxial with joint 34. Joint 34 attaches to either a linear bearing(free to travel along the line connecting the endpoints of the springlever 25) affixed to the spring lever, or to a straight-line “Watts”linkage 70, details of which are shown in FIG. 1b , consisting of thelinks 60, 61 and 62 and connecting joints 36, 37, 38 and 59. The armassembly 12 will not move if the spring lever 25 attaches directly tojoint 34 without some form of linear bearing/prismatic joint orstraight-line linkage. Left spring lever 53 is attached to the right armassembly via joints 55 and 56 in conjunction with a similar Wattslinkage.

The left arm assembly 12 is actuated via torque applied to left chaindrive sprocket 41 at joint 32. Sprocket 41 engages the output shaft 29of the arm motor 27, which is centrally mounted within the left armend-link 30. The right arm assembly 14 is similarly actuated, with rightchain drive sprocket 39 engaging the output shaft (not shown) of rightarm motor 51, which is mounted within right arm end link 47.

Two extension springs 5, 52 connect the two arm assemblies. Left spring52 connects the proximal end of the left arm spring lever 25 at joint 35to the right spring pre-tension pulley 54 (visible in FIG. 3) of theright assembly. Similarly, right spring 5 extends between the proximalend of the right arm spring lever 53 and the left spring pre-tensionpulley 26. Spring tension may be adjusted by rotating the springpretension pulleys 26, 54 in the appropriate direction. Such adjustmentcan be accomplished by applying torque via the arm motors 28, 51 whiletheir respective arm motor clutches 28, 44 are disengaged. Since the armmotor output shaft 29 (right shaft not shown) has a finite range oftravel, this will eventually result in rotation of the arm motor body28, 51, which engages the respective spring pre-tension pulley 26, 54via a single-stage spur gear transmission.

FIG. 4 illustrates possible modes of operation of the inventive robot.Using the combination of the independently-driven wheels 6, 8, theleadscrew 20 and the independently actuated arms 12, 14, the robot canuse one or a combination of motions to perform useful functions duringoperation of the vehicle. Horizontal roving (a) is effected when theleft and right drive wheels are rotated in the same direction to tiltthe leg forward. The wheels continue driving in the same direction tomove the vehicle forward with the end of the leg on the support surface.To steer, the wheels may be operated in opposition to each other. Theindependent operation of the wheels allows the robot to be turnedquickly on a point, or with a very small turning radius. As can be seenin the perspective view of FIG. 13, horizontal roving mode gives thevehicle a low vertical profile, allowing it to pass easily beneath lowobstacles, such as fences, wires, or low shrubs, and to avoid opticalsensors that may be positioned several inches or more above the floor orsupport surface.

An uprighting maneuver (b) from the horizontal roving mode involvesapplying a sudden strong torque to the wheels in the appropriatedirection. When reaction wheels are torqued in one direction, thevehicle experiences an equal-and-opposite reaction torque. Asillustrated, a strong clockwise torque induces a counter-clockwiserotation of the leg to rotate the leg into a vertical position. Themotion of the reaction wheel itself can later be bled back off, eitherwith reaction control thrusters, or merely when the vehicle comes backin contact with the support surface. The instantaneous torque availablewhen using reaction wheels is limited to that provided by the motor usedto drive the reaction wheels themselves. In the upright mode, the robotdrives only on the reaction wheel wheels, with the leg pointed upward toproviding a raised support frame for mounting vision systems or othersensors to expand the sensor's range for surveying the surroundings.

For upright balancing and roving (c) in the fore-aft direction,toe-balancing (e) and hopping (d), reaction-wheel stabilization may beused. The reaction wheels can be used as counterweights in theleft-right direction (akin to a tight-rope walker's balance bar).Finally, the reaction wheels may act as counterweights for the stiffelastomer spring to work against in order to achieve the actual hoppingmotion of the vehicle in either conventional monopedal locomotion (f) orcartwheeling monopedal locomotion (g).

The mass of the wheels should be significant in order for the last threeof these functions (e, f and g) to be viable. In the exemplaryembodiment, the mass of each of the wheels is provided by the vehiclebatteries 7, which are distributed symmetrically around the outer hub ofeach wheel, and the motors 45 (within their corresponding motor housings9) that are used to drive the wheels 6, 8. By exploiting the weights ofthese relatively heavy components as opposed to adding dead weight tothe wheels, the overall mass of the robot can be minimized.

The independently-actuated arms 12, 14 can function both as a hoppingmechanism when rotated symmetrically about the central leg 16 (aroundthe roll-axis) and as an actively-controlled roll-axis stabilizer whenrotated anti-symmetrically about the central leg. A hopping motion,shown in FIG. 5a , is created by, starting from a configuration with thearms angled downward (indicated by grey lines in FIG. 5a ), rapidlyrotating the arms 12, 14 symmetrically upward relative to the leg 16,abruptly stopping as they reach a horizontal orientation. One or morelevel sensors (not shown), which may be located on the arm assemblies12, 14 and/or on the leg 16, may be used to generate electrical signalsthat are communicated to the vehicle's controller (not shown). In anexemplary embodiment, the controller may be incorporated in one or morecustom and/or commercial off the shelf (COTS) printed circuit boards(PCBs), such as the C200 MCU available from Texas Instruments. The PCBswill preferably be enclosed within a protective housing that can beattached to the leg 16 in a way that does not interfere with operationof the leadscrew. Feedback from the level sensors may be used to controlthe anti-symmetric arm motion for balancing. As illustrated by FIG. 5b ,anti-symmetric arm motion generates an equal and opposite torque aboutthe leg 16, enabling feedback stabilization about the roll-axis.Appropriate superposition of these two motions allows the robot tosimultaneously stabilize and hop in the roll-axis plane. The majority ofthe vehicle's mass should be concentrated at the ends of the arms inorder for the arms to effectively hop and balance the vehicle.

In the preferred embodiment, the leg 16 should be formed from a materialthat is light while maintaining sufficient stiffness to avoid bucklingor introducing excessive structural flexibility. Lightweight steel,aluminum and titanium are examples of appropriate materials.

When out of ground contact, the wheels 6, 8 provide pitch-axis stabilityby actively applying torque, using the same principle as theanti-symmetric action of the arms. The arm assemblies 12, 14 areconfigured in a parallelogram linkage so as to maintain constant angularalignment of the wheels 6, 8 relative to the central leg 16 throughoutthe arm's range of motion. This simplifies the overall dynamics bypreventing strong coupling between the pitch- and roll-axis dynamics. Inthis configuration, the top and bottom arms 18, 22 and 19, 23,respectively, preferably have an outward curvature at their lengthwisecenters, as shown, in order to prevent interference between coplanarcomponents. In other words, the ends of the arm sections curve inwardrelative to their midpoints. A simpler configuration in which the wheelsare directly attached to a single link would function similarly forsmall angular deflections (+/−15 degrees) of the arms.

In the preferred embodiment, the left and right arm motors 28, 51 arehigh-speed/low-torque in order to optimize hopping performance. The armsare spring-loaded by extension springs 5, 52 to support the weight ofthe arms and to recover energy during hopping. While this springmechanism should strongly resist motion of one arm relative to the otherin order to support the weight of the wheels during hopping, it shouldnot substantially resist rotation of either arm relative to the centralleg 16. This arrangement allows the anti-symmetric rotation necessaryfor active roll-axis stabilization.

While placing a torsion spring across the arms fulfills these basicrequirements, additional functionality can be realized via a moreintricate linkage mechanism. Specifically, since each arm is actuated bytorque applied at one of the outward joints by the correspondinghigh-speed/low-torque motor 28, 51, a digressive stiffness (decreasingwith increasing deflection) is desirable in order to provide a moreconstant resistance to symmetric motion; i.e., provide high support atsmall deflections, without overwhelming the motors at large deflections.Secondly, in order to facilitate multimodal operation, the effectivespring rate is preferably adjustable on-the-fly, without introducingtorsional bias/asymmetry. Lastly, in order to store energy for largejumps (and to keep the vehicle in a folded configuration during roving),the arms should preferably self-lock into a fully-tensioned statewithout requiring additional actuators. Furthermore, the angulardeflection at which locking occurs must be less than 90 degrees in orderto prevent collision between coplanar mechanism links.

In the preferred embodiment, the self-locking feature is achieved byincorporating a pair of non-coplanar springs 5, 52 attached to springlevers 25, 53 within the parallelogram linkage. The relationship betweenthe springs 5, 52 and levers 25, 53 is illustrated in FIG. 7, whichshows how the top plane and bottom plane function separately andcombined (right). The top plane, shown on the left in FIG. 7, includesright spring 5, left spring lever 25, and joint 34′, which includesjoint 34 and Watts linkage 70. The bottom plane, shown in the center ofthe figure, includes left spring 52, right spring lever 53, and thejoint corresponding to left joint 34′, which includes joint 55 and itsassociated Watts linkage (or other appropriate linkage.) The black dotsin the line drawing correspond to the respective joints identified inFIGS. 1-3. FIG. 8 illustrates the kinematic equivalent realizations ofthe arm suspension mechanism shown in FIG. 7.

As illustrated by the curves plotted in FIG. 9, the resistance tosymmetric motion decreases with increasing deflection from horizontal,(arms outstretched, as in FIG. 1), measured as angular displacement(α_(L)=−α_(R) [deg]), and eventually changes sign past a certaincritical angle (“0” in the plots). This causes the arms to lock into afully tensioned state, provided that the arms are constrained to deflectat most slightly past this critical zero-torque angle. In FIG. 9,angular displacement is plotted relative to percentage spring stretch,resultant torque (in Newton meter), and effective torsional spring rate(in Newton meter/radian), respectively, at four different levels ofspring pre-tension. FIG. 10 illustrates the resistance to anti-symmetricrotation under varying levels of spring pre-tension using the samecomparisons used in FIG. 9. FIG. 11 is a plot of the criticalzero-torque arm (locking) angle as a function of varying link lengthsfor symmetric rotation, where B/L=0.125, C/L=1.094, and D/L=0.438.

Note that the symmetric configuration enables bi-directionalseries-elastic actuation using the extension spring. Referring to FIG.12, during conventional operation, the main body of left arm motor 28 isheld stationary by a small actuated clamp 62. Loosening clamp 62 allowsthe motor 28 body to rotate. This, in turn, drives left springpre-tension pulley 27 around which the one end of extension spring 25 iswound. Similarly, right arm motor 51 may be rotated by loosening itscorresponding clamp (not visible in the figures) to drive rightpre-tension pulley 54 to adjust the tension on spring 5. These featuresallow the springs to be pre-tensioned while the arms 12, 14 are lockedat the maximum extent of travel by loosening the clamps 62, and drivingthe motors 28, 51 in the direction that causes downward arm motion (inorder to prevent unlocking). Note that, since the springs 5, 25 arealways in tension, they may be tightened by driving the correspondingpulley 27, 54 in either direction. Additionally, the motors 28, 51 mayactuate in series with the springs 5, 25 by loosening the clamps. Thisis sometimes referred to a “series elastic actuation” and may be usefulfor buffering mechanical energy, and isolating the motors 28, 51 frommechanical shock.

As described above, each drive wheel 6, 8 has two wheel motors thatpropel and steer (via differential drive) the vehicle when in contactwith the support surface. Referring to FIGS. 1 and 2, on right drivewheel 8, two wheel motors 45 are fixed on the wheel hub via housing 9.The drive gears of motors 45 engage spur gear 40, which is mounted onaxle 46. As previously mentioned, the batteries 7 are located on eachwheel hub to provide the added weight needed for balancing, hopping andmonopedal motion. On the left side, drive wheel 6 has two motors 45 thatdrive spur gear 42 to rotate the wheel around its corresponding axis.

In an alternative embodiment, the drive wheels may be replaced by asecond set of arms mounted in an orthogonal arrangement with the armassemblies 12, 14. This provides a pitch-axis arm pair and a roll-axisarm pair. In this embodiment, level sensors may be provided within boththe pitch- and roll-axes to provide the feedback needed to controlanti-symmetric arm motion within both axes. The resulting structure canprovide highly stable monopedal locomotion that can balance in multipleaxes. Since the weights of the wheels and their corresponding drivemotors are eliminated in this embodiment, additional weight may need tobe added to the end of each arm assembly to provide the mass needed forhopping and toe balancing.

The multimodal robot of the first embodiment can be fitted with optical,audio, thermal, chemical and other environmental sensors, or acombination of different sensors, which can be used to provide inputinto an adaptive system controller, e.g., artificial intelligence toallow the vehicle to develop a situational awareness that will permitpredictive path planning in complex environments. Alternatively, or inaddition, the vehicle can have incorporated into its electronics atransceiver for receiving remote commands and for transmittinginformation collected by its sensors.

The robotic system described herein is useful for maneuvering withincomplex structures or rugged terrain via different combinations ofhopping, pole climbing, toe balancing, horizontal roving and uprighting,all in a controlled fashion. For example, the robotic system can climbstairs using a combination of pole climbing and toe balancing to climbstairs.

Second Multimodal Robot Embodiment

A second multimodal robot 100, illustrated in FIGS. 14, 15 and 20, is atreaded vehicle that can perform stable both heel and toe standing,i.e., “wheelies” and “stoppies”, and can balance on the edge of a stepor similar change in elevation. As shown in FIG. 14a , multimodal robot100 includes a pair of arms 110 and 120 which comprise independent treadassemblies that are attached to chassis 102 by way of tread shaft 108.In the exemplary embodiment, a single chassis holds the actuators,sensors, electronics, and batteries required for operation andcommunication with the robot. Rotation of the shaft 108 causes the treadlinks to advance for translational movement; rotation about the shaftcauses the entire tread assembly to rotate with respect to the chassis.This unique “hip joint” is described in more detail below. An optionalplatform 104 may be attached to chassis 102 to provide a support forattaching sensors, cameras, or other equipment or instruments to betransported on the robot. Where no platform is provided, a housing maybe provided to enclose the chassis and any associated electronics,batteries or actuators. If a platform 104 is included, the chassishousing and platform can be the same structure (as illustrated, chassis102 is separated from platform by a dashed line), or the chassis housingcan be fully or partially enclosed within the platform. It should benoted that platform 104 is not limited to a rigid structure—it may be arigid or a deformable body which may be passively or actively deformedto adapt the robot as required for a particular task. Further, theplatform need not be a solid, enclosed structure, but can be an openframe or a combination of open and closed portions.

One or more sprockets may be driven with an actuator such as a motor,engine, or pneumatic or hydraulic turbine. As illustrated in FIG. 14b ,which is a simple diagram showing the components of a tread assemblywith a side cover removed, each tread assembly includes two or moretread sprockets 114, 116 rotatably mounted in the same plane on avertical side plate or frame 111 to engage tread 112. One or more treadguides 115 may also be rotatably mounted on frame 111. Tread sprocket114 is mounted coaxially with shaft 108. One or both sprockets 114 maybe mounted with a sensor to measure position, speed, and/or torque. Aforce or pressure sensor may optionally be provided underneath a span ofthe tread 112 to detect where the tread assembly is in contact with theground or other surface. Mechanisms as are known in the art foradjusting the tension of the tread may also be included. Controlelectronics, batteries, and communications electronics may be mountedwithin the tread arm 110, or may be housed within chassis 102 orplatform 104, if appropriate.

Referring briefly to FIGS. 20b and 20c , wheels 124 may be rotatablymounted near the edge of platform 104, opposite the chassis, to furtherexpand the robot's functionality. For example, in FIG. 21a , the robotis shown maneuvering within a duct 128 or other narrow passageway byeffectively wedging itself between opposite sides of the duct. Thewheels 124 allow the robot to apply pressure perpendicular to the sideof the duct as the robot moves forward along the length of the duct.Sensors within the treads or attached to the tread shaft are preferablyincluded to provide feedback to allow the robot's controller to adjustthe relative angles of the chassis and treads to maintain the pressureneeded to allow the robot to progress through the duct or passageway.The wheels 124 may be attached to freely rotate around their axles, orthey may be attached to the drive shaft of one or more additional motorsfor providing an additional degree of control.

A variation on the embodiment of FIG. 14a is illustrated in FIG. 17,where the tread assemblies are replaced with a corresponding wheelassembly, which includes two or more wheels 117, 118 rotatably mountedin a planar relationship on the arms 119. In this embodiment, a drivechain or other linkage should be provided to drive wheels 117 and 118together in order to perform toe balancing or other maneuvers thatrequire force to be applied at the distal or toe end of the arm 119.Axle 108 extends from chassis 102 as above to drive wheels 118. Thefollowing descriptions of the robot's “hip joint” and maneuvers enabledthereby are equally applicable to the treaded version of FIG. 14a andthe wheeled configuration of FIG. 17.

Referring to FIG. 19, in the preferred embodiment, a two degree offreedom joint is used in the mobile robot of FIG. 14a to connect eacharm 110, 120 (or 119 in the wheeled version), to the chassis 102 andtransmits two decoupled, yet coaxial, torques. The torque to advance thetreads 112, 122 (or rotate the wheels) is transmitted by coupling thetread shaft 108 on one end (via coupling 138) to a motor 140 and on theother to the drive sprocket 114 (or wheel). This shaft passes through,and spins freely relative to, a tread gear 130, which is rigidly mountedto the arms 110, 120 (or 119). A pinion gear 132 mounted to a secondshaft 136, parallel to the tread shaft 108, causes the pinion gear 132,and arms 110, 120 (or 119), to rotate with respect to the chassis 102when driven (via coupling 138) by the second motor 142, which may alsobe referred to as the boom motor. This assembly provides for theadjustment of the center of gravity, as will be discussed in more detailbelow. A slip ring 144 (with one or more channels) may be locatedcoaxially with the first shaft 108 in order to transmit and receivepower and/or electrical signals between the chassis 102 and arms 110,120 (or 119) throughout a continuous range of rotation. Optical encoders134 may be included to measure the angle of the chassis with respect toarms 110, 120 (or 119) to provide feedback to the control system. In analternative configuration, the components of the hip joint, i.e., allmotors, gears and sensors, may be located in the arms, such that thechassis can simply be an axle that joins the shafts 108 of two arms 110,120 or 119 together.

The embodiments of FIG. 14 and FIG. 17 are capable of independentlyrotating the arms 110, 120 (or 119) with respect to the chassis 102 inaddition to driving the treads 112, 122 (or wheels 118). This allows therobot to dynamically adjust its center of gravity.Commercially-available MEMS accelerometers and gyroscopes, coupled withadvanced filtering techniques, allow the robot to estimate its anglewith respect to gravity. With the arms 110, 120 unfolded away from thebody, the inventive multimodal robot can balance upright on the distal(with respect to the tread shaft 108) end of the arms, as illustrated inFIGS. 15b and 20c , making it possible to significantly expand the rangeof an on-board sensor or instrument, such as a camera. An exemplaryrobot with tread assemblies on the order of 10-15 cm high and 30-50 cmlong may be able to stand up to 65 cm tall and overcome obstacles thatwould otherwise be insurmountable with a 10-15 cm tall treaded robot.The inventive design is also capable of both crossing chasms nearly aswide as the vehicle by extending the arms in opposite directions, asillustrated in FIGS. 15c and 20b . Further, the front-mounted pivot ofthe chassis may be used to actively dampen vibrations when drivingquickly over rough terrain. The reconfigurability of the arms permitsseveral modes of locomotion, which the inventive robot can switchbetween based on the type of terrain encountered. As illustrated in FIG.15a and FIG. 20d , the robot can balance on the proximal (with respectto the tread shaft 108) end of the arms, i.e., perform a wheelie, withthe proximal end of the arms 110, 120 in contact with the ground andneither the chassis 102 nor the distal end of the arms in contact withthe ground. This can be referred to as the “V-mode”. The angle betweenthe chassis 102 and the arms 110, 120 may be changed by actuating theboom motor where the tread motor will be actuated as needed to keep thechanging center of gravity over the contact point to keep the robot fromfalling over. This change in angle may be the result of a referencecommand sent by an operator or performed automatically by the robot inresponse to an external stimulus or as part of a programmed sequence.This maneuver can be used to initiate a climbing sequence, for example.In FIGS. 15b and 20c , the robot is illustrated in a toe balance, or a“stoppie”, which is performed by placing the distal end of the arms 110,120 in contact with the ground and neither the chassis 102 nor theproximal ends of the arms in contact with the ground. This can bereferred to as the “C-balancing mode.” The angle between the chassis 102and the arms 110, 120 may be changed by actuating the boom motor wherethe tread motor will be actuated as needed to keep the changing centerof gravity over the contact point. This change in angle may be theresult of a reference command sent by an operator or performedautomatically by the robot in response to an external stimulus or aspart of a programmed sequence. The multiple modes of locomotionaccording to the inventive mechanical design coupled with feedbackcontrol algorithms will enable the robot to overcome complex terrain,such as stairs, rubble, and other obstacles while retaining a small formfactor to navigate in confined spaces and to reduce cost and weight. Ina preferred embodiment, the on-board electronics includes wirelesscommunication circuitry, as is known in the art, to enable bidirectionalcommunication over WiFi. In an especially preferred embodiment, therobot includes appropriate electronics and programming to enable therobot to communicate with one or more computers, other robots, andmobile devices, such as a cellular telephone by using, for instance, theIEEE 802.11g standard.

Examples of complex tasks that can be performed by the treaded/wheeledrobot are illustrated in FIGS. 21a , which was discussed above, and FIG.21b , which illustrates a portion of a stair climbing maneuver as wellas showing how the treaded robot is capable of “perching” on smallsurfaces, such as the edge of a stair (126), a branch, or a telephone orpower line. In this configuration, the treads of the robot are incontact with the surface at one point and the robot maintains itsbalance by adjusting the chassis and/or boom to keep its center ofgravity in line with the contact point. Inertial sensors (e.g.,accelerometers and gyroscopes) may be used in conjunction with contactsensors (e.g., force sensitive resistors) inside the tread assemblies todetermine the contact point. Active balancing provided by thecombination of the tread and balancing motors and continuous feedbackfrom the sensors to control the motors maintains the robot's center ofgravity to stabilize it sufficiently to hold its position. The center ofgravity is shifted in the desired direction when the robot is made toclimb up or climb down the stairs 126 so that the center of gravity iskept directly above the contact point using a combination of modes ofmovement.

FIGS. 22a and 22b illustrate one example of operations that may beperformed by the above-described multimodal robot for climbing anobstacle such as a staircase. In step 160, the robot approaches the stepwhile balancing on the distal end of the arms (in “C-balancing” mode, asillustrated in FIGS. 15b and 20c ). In steps 162 and 164, upon arrivingat the step, the position of the chassis is adjusted such that thecenter of mass is directly above the edge of the first step. In steps166 through 174, via a coordinated combination of tread actuation andappropriate variation of the angle between the treads and the chassis,the robot balances on the edge of the step while gradually edging up thestep.

In one realization of this maneuver, the angle between the treads andthe chassis is actuated as a function of time based on what is required,nominally, to keep the center of mass over the edge of the step whilemaintaining the desired angle between the chassis and horizontal, whilethe contact point between the treads and the edge of the step moves(relatively slowly) along the arm; balancing is then achieved viafeedback control applied (relatively quickly) via tread actuation. In asecond realization of this maneuver, feedback control is applied via acoordinated application of both tread actuation and small adjustments tothe angle between the treads and the chassis.

Upon reaching the top of the step, there are two possible scenarios: Thefirst is that vehicle has either reached the top of the stairs, or theangle of the edges of successive steps from horizontal is less than theangle of the chassis from horizontal (that is, the angle of the steps isrelatively shallow). In either situation, the vehicle simply returns toC-balancing mode upon reaching the top of the step and continues itsforward movement. If it reaches another step, the situation isequivalent to that depicted in step (1).

The second scenario is that the vehicle has not reached the top of thestairs, nor is the angle of the edges of successive steps fromhorizontal relatively shallow. In this case, the angle of the chassisfrom horizontal as the vehicle nears the top of the current step may beplanned to be nearly the same as the angle of the edges of successivesteps from horizontal. By planning the maneuver in this manner, theproximal end of the vehicle will reach the edge of the next step whilestill in contact with the edge of the previous step, as in step (8). Thecenter of mass may then be adjusted to be over the edge of the nextsteps (9) and (10), and the process described in steps (4) through (7)is repeated, as illustrated in steps (11) through (15).

Various combinations of the above steps can be used to maneuver therobot into positions for performing a desired task. The inventive robotis able to perform this and similar tasks because it operates, or can beoperated, to shift its center of gravity to balance on a small point bychanging the angle between the arms and the chassis, and by using thetreads or wheels to “catch itself” before it falls.

The multi-modal robot of the second embodiment is capable of performinga wide variety of maneuvers with the minimal set of actuators, thussaving cost and weight. Additional sensors can be mounted internally orexternally, such as contaminant sensors, Global Positioning System (GPS)receivers, wind sensors, analog or digital cameras, optical or radiationsensors, among many other possible uses. End effectors may be mounted onthe mobile robot platform 104 or arms 110, 120 or 119, such as linkagemechanisms with a gripper, solid or liquid collection systems, lightingsystems, or weapons systems, among many others.

An alternative configuration of the second multimodal robot embodimentis illustrated in FIGS. 16a -c. In this configuration, shifting of thecenter of gravity is still used, however the manner in which theshifting is effected is different.

In this embodiment, the robot includes a chassis 148 and an actuatedboom 150. The chassis 148 is driven by a pair of treads 152, 154 (orconventional wheels 156 may be substituted, as shown in FIG. 18). Theboom 150 has significant mass. In the exemplary embodiment, the mass ofthe boom is approximately equal to the mass of the chassis. As in theprevious embodiment, motors are configured on the robot to drive thetreads (or wheels) and to change the angle of the boom 150 with respectto the chassis 148.

The hip joint described above with reference to FIG. 19 may also beincorporated in the configuration that uses a boom for shifting thecenter of gravity. In this case, the boom motor (which corresponds tothe balancing motor) will activate rotation of the boom arm.

The second multimodal robot embodiment includes sensors to detect therobot's configuration. Feedback control is applied to enable the vehicleto balance on its front or rear cogs (or wheels). The vehicle can alsoclimb obstacles (including stairs) by extending the mass of the boom 150over the obstacle and rotating the chassis up and over. This maneuvermay be done in a statically stable manner or in a dynamically balancedmanner. The boom arm may be extensible and/or may itself be configuredwith wheels or treads, in a manner similar to the wheels 126 in theprevious configuration.

As in the first multimodal robot embodiment, the configuration with theboom 150 takes advantage of the weight of the batteries for use as afunctional mass. An electrical connection is made between the boom andthe chassis to transmit the power from the batteries to the motorshoused within the chassis. In the exemplary embodiment, this connectionis made with slip rings, steel shafts riding in bronze bushings, as inthe hip joint describe above. The slip rings allow the boom to berotated about the chassis with no angular limitation.

In this configuration, the treads of the robot are in contact with thesurface at one point and the robot maintains its balance by adjustingthe boom to keep its center of gravity in line with the contact point.Inertial sensors (e.g. accelerometers and gyroscopes) may be used inconjunction with contact sensors (e.g. force sensitive resistors) insidethe tread assemblies to determine the contact point.

The second multimodal robot embodiment uses multiple commercialoff-the-shelf (COTS) sensors (MEMS-based accelerometers and gyroscopes,and optical encoders 134 (shown in FIG. 19) to estimate the angle of thechassis with respect to gravity (in the configuration of FIG. 14) andthe angle of the boom arm with respect to the chassis (in theconfiguration of FIG. 16). The programming of the robot includes acontrol system (which may include a Kalman filter) to actuate the motorsto dynamically balance the robot. The current prototype also acceptsmanual input via a COTS radio frequency remote.

In one application of the second multimodal robot embodiment, an “army”of the robots was deployed in an open, paved area (a parking lot) aroundwhich plumes of colored smoke were released. Each robot was equippedwith a sensor pack and electronics to measure smoke concentrations andwind velocities. The measurements were transmitted in real time (viaWiFi and 3G cellular data links) to an off-site supercomputer runningadvanced weather-forecasting type algorithms. These algorithms, in turn,synchronized a numerical simulation of the smoke plume with the actualmeasurements taken in the field in real time (a problem known as dataassimilation), then told the vehicles where to move next in order tominimize the uncertainty of the forecast. The goal of the system, whichwas successfully realized in the experiment, was to forecast where thesmoke was going to go, as precisely as possible, before it got there,while coordinating the vehicles in real time to collect the mostvaluable information possible for the particular wind conditions presentduring that test. The research has important social relevance related tonew technology and algorithms for tracking a wide variety ofenvironmental plumes of interest, from gulf-coast oil, to Icelandicvolcanic ash, to possible chemical/radioactive/biological plumes inhomeland security settings.

Third Multimodal Robot Embodiment

In a third embodiment, a spherical robot incorporates momentum exchangedevices to achieve rapid acceleration or deceleration in any direction.

As illustrated in FIG. 23, an exemplary embodiment of the sphericalrobot according to the present invention includes a frame 202 forsupporting a plurality of momentum-exchange elements 204 so that theelements are distributed relative to the surface of a spherical shell210 that encloses the frame 202, elements 204, and all controlelectronics, actuators and batteries that are required to power andcontrol the robot. Sensors may also be included to provide feedback tooptimize balancing and locomotion under different conditions. Thecontrol electronics may include wireless communication devices forcommunication with a remote computer, mobile phone or other wirelessdevice. Alternatively, the spherical robot may be tethered to acontroller, such as a joystick, track ball or the similar externalcontrol device.

The basic elements of three different momentum exchange elements thatmay be used in the spherical robot are shown in FIGS. 24a -24 c. Thereaction wheel assembly (RWA) shown in FIG. 24a includes a single motorfor spinning the wheel. A single gimbal control moment gyro (SGCMG) isshown in FIG. 24b . This assembly includes two motors, one for spinningthe wheel, the other for rotation of the gimbal, allowing the directionof the wheel angular momentum to be varied. In FIG. 24c , a doublegimbal control moment gyro (DGCMG) is shown, with three motors,including the two used in the SGCMG plus a third motor to vary the planeon which the SCGMG sits.

In the configuration of the fourth embodiment that is shown in FIGS. 23and 26, a cubical frame 202 is populated with four single-gimbal CMGs204 a-204 d, with each gimbal axis 206 a-206 d at an angle extendingacross each of four faces 208 a-208 d. This makes the inventive robotparticularly agile, as the momentum needed to maneuver is stored withinthe SGCMGs and, thus, does not need to be generated by high-torque,large electrical power-consuming motors as in standard direct drivesystems of the prior art. The SGCMGs may be operated individually orsimultaneously to effect the desired function, such as rolling,steering, stationary rotation around the contact point or balancing inposition. While frame 202 is shown in a cubical configuration, it may beconstructed with virtually any geometric shape that fits within aspherical shell, including pyramidal, conical, symmetric, skewed, lineararrangements combined with 3-D structures, and various othercombinations of such shapes. FIG. 25 illustrates a few of a largevariety of possible arrangements of momentum exchange elements,including a pyramid, skewed cone, symmetrical octahedron, and roof-typewith linear combinations of elements. Virtually any geometrical shapecan be used that will allow momentum to be generated in a plurality ofdifferent directions for steering, rolling, balancing, etc. Further, therobot is not limited to spheres as an outer structure, but may includegeneralized amorphous ellipsoidal configurations as well.

The shell 210 that is used to enclose the frame, momentum exchangeelements, the actuators and control electronics may be formed from awide range of materials, selection of which will depend on the intendedapplication and will be within the level of skill in the art. Ingeneral, the outer surface of the shell should be capable of generatingsufficient friction with the surface on which the robot will be movingto efficiently convert the action of the momentum exchange elements intomotion in the desired direction. The material may be a rigid, preferablyimpact-resistant plastic or polymer, which may include carbon-fiber orfiberglass, among others. In some applications in harsh environments,metals, metal-composites, or specialized materials such as KEVLAR®composites, may be appropriate for particularly hazardous applications.In other applications, it may be appropriate to use a layered structurethat includes padding for shock absorption, thermal insulation or otherprotective covering, such as NOMEX® or other fire-retardant materialthat can be incorporated in or underneath a hard exterior shell.

FIG. 26 provides a three-dimensional drawing of an exemplaryimplementation of the inventive spherical robot. As illustrated, theframe 202 should fit snuggly within the spherical shell 210. For theexample of a cubic frame, the corners of the frame may be chamfered, asshown, to provide a broader, angled and somewhat rounded surface tocontact the inner surface of the shell (as opposed to having sharpcorners on the frame). This provides uniform structural support for theshell 210 while ensuring that the frame 202 and the components mountedthereon are stably supported, i.e., so that the frame does not moverelative to the shell.

As illustrated, each SGCMG 204 a-d incorporates the spin motor (theshaft of the spin motor 220 can be seen in FIG. 26) and reaction wheelwithin a small, flat cylindrical housing, which is fixedly mounted onthe corresponding gimbal axis 206 a-206 d. Power for driving the spinmotor is provided through wires running through the corresponding gimbalaxis. One end of each gimbal axis is attached the shaft of a gimbalmotor 222, while the other end of the axis is supported within a pivotso that the axis and reaction wheel rotate when driven by theircorresponding gimbal motor.

All electronic components for operating, communicating with, andcollecting data, if appropriate, including all wiring and connectors,will be housed within shell 210, preferably centered within frame 210 toplace the weight at the center of the sphere. The components, which mayinclude one or more printed circuit boards with associated batterycasings or other holders, may be supported on a bar or plate thatextends between opposite corners of the cube or between the upper face208 e and lower face 208 f of the cube as illustrated, so as not tointerfere with movement of the elements 204. Some of the components,e.g., the batteries, may alternatively be mounted within the insideedges of the frame if the frame is hollow. In an alternative embodiment,elements 204 may be mounted on all 6 faces of the cube, or on all facesof a selected geometric structure, as long as sufficient space isprovided to avoid interference between movement of momentum exchangeelements and other components of the system.

FIGS. 27a and 27b illustrate an alternative construction of thespherical robot with the outer shell removed. In this case, the frame232 is formed by the intersection of four open-centered disks 234 a-dthat correspond to faces 208 a-d of FIGS. 23 and 26. The rounded facesprovide additional structural support for the spherical shell. The tophousing 236, which encloses the control electronics is attached to thetop of frame 232.

Referring to FIG. 27b , which shows an exploded view of the fullassembly with one SGCMG also in exploded view, the frame is defined bythe assembly of faces 234 a-234 d with top plate 244 and bottom plate245, which are attached by brackets 242. In addition to the top housing236, attached to the upper surface of top plate 244 are a number ofbattery holders 240 for retaining batteries 238. As illustrated, thebatteries are button style lithium batteries. Additional battery holders240 and batteries 238 are located on the outer surface of bottom plate245 along with the gimbal motor controllers 246.

FIG. 27c shows an exploded view of SGCMG 250 shown in FIG. 27b . Therotor 268 is attached to the rotor shaft 270. The rotor provides theinertia for the momentum storage of a SGCMG. The rotor and rotor shaft268, 270 are held in place relative to the outer housing formed from thecombination of 256, 259, 260, 267, 272 and 278, by a journal 252, 277and thrust bearing 258, 271 combination. The shaft of the spin motor 254is attached to the rotor shaft 270 and the spin motor 254 is attached tothe c-ring 252, which is also attached to the bottom plate 256 of thehousing. The spin motor 254 rotates the rotor 268 at a constant rate (inthe SGCMG case) or varies the angular rate (in the VSSGCMG case) viafeedback from the optical encoder 280 and spin motor electronics 282.The rotor speed is measured by the optical encoder 280, which isattached to the top plate 276 of the housing. The spin controlelectronics 282 are mounted to mounting posts 279, which are alsoattached to the top plate 276 of the housing. The housing assembly 256,259, 260, 267, 276, 278 is attached to gimbal shafts 269,273. One gimbalshaft 269 is attached to a spur gear 262, which is free to rotaterelative to the right gimbal mounting bracket 264 via a thrust/journalbearing combination. This spur gear 262 is kinematically constrained toa second spur gear 263 which is attached to the gimbal motor 261 and isalso free to rotate relative to the right gimbal mounting bracket. Thesecond gimbal shaft 273 is rigidly attached to the slip ring assembly274 and is free to rotate relative to the left gimbal mounting bracket276 via a thrust/journal bearing combination. The slip ring assembly 274provides power (in spite of the continuous rotation of the gimbal) tothe spin motor controller 282. The angular rotation of the gimbal shaft273 is measured by a potentiometer 275 whose movable part is attached tothe gimbal shaft and immovable part is attached to the left gimbalmounting bracket (28). The left 276 and right 264 gimbal mountingbrackets are attached to the sidewall 234 a.

In one embodiment, the spherical robot may have pressure bladdersattached on the inner surface of the shell 210 or on non-interferinglocations on the frame 202. (A single exemplary pressure bladder 214 isdiagrammatically illustrated in FIG. 23). The bladders will preferablybe uniformly distributed around the inner surface of the shell, e.g., onthe edges of two opposite faces of the cube, to control buoyancy,thereby allowing the robot to float on the surface of a liquid, e.g., anatural or artificial body of water, or to move fully- or partiallysubmerged below the surface. Operation of the momentum exchange elementswill allow the buoyant robot to move within or over the surface of thebody of water as the robot spins, thus providing an amphibious vehicle.In one implementation, the bladders may be pre-filled to the desiredbuoyancy prior to deployment of the robot via a valve accessible throughthe shell. In another approach, small compressed gas canisters, as areknown in the art for use in life vests and buoyancy compensators, may bemounted on the frame in communication with a feedback system that willdetermine the conditions in the body of water, e.g., temperature,surface turbulence and weather conditions, and control the amount of gasreleased into the bladders to achieve the desired buoyancy and frictionwith the water's surface to maneuver effectively and efficiently. Bleedvalves on the bladders may also be provided to actively adjust thebuoyancy as needed under changing conditions. The gas canisters may bereplaced with new canisters after one or more uses.

Alternatively, the robot can be made passively buoyant through materialselection. For example, the frame can be constructed using a lightweightmaterial such as plastic, wood or fiberglass, or using lightweightmetals such titanium or aluminum when the strength and durability ofmetal is required. The material used for the frame can also be hollow orpartially-hollow, e.g., honeycomb structures or extruded channel. Theshell, which would need to be a continuous surface without any openingsto make it watertight, could be a formed from a buoyant plastic orpolymer, such as polystyrene, neoprene or closed cell foam. The buoyantfoam structure could be covered with an impervious outer skin orcoating, such as a lightweight metal, for applications where metal ispreferred, or an epoxy resin or other polymer, using a constructionsimilar to that used in typical surfboards. Openings (ports or doors) inthe shell for accessing the interior components of the robot would needto be sealable to produce a watertight closure.

FIG. 28 provides a block diagram of an exemplary control architecturethat can be used with the spherical robot. As will be recognized bythose in the art, other control architectures can be use. The pathgeneration block can be achieved by the relationship between thevelocity of the body and the angular rate. The ACS control law block,pseudoinverse CMG steering law block, and gimbal angular rate controllerblock can be derived using procedures and algorithms that are known inthe art.

Locomotion within a body of liquid can be achieved by activating themomentum exchange elements to rotate the robot's body in the directionof desired motion, the same as would be used on land. FIGS. 29a-cillustrate different applications of the spherical robot. Using a seriesof cartoons depicting an exemplary robot with a single RWA, FIGS. 29aand 29b illustrate a free-surface case and a near-a-surface case,respectively. In FIG. 29a , in a fluid, when the RWA spins one direction(counter-clockwise as shown), the sphere spins in the opposite direction(clockwise as shown). The fluid's interaction between the rotatingsphere and the free-surface causes the sphere to move in translation tothe left, as dictated by known analytical solutions to the Navier-Stokesequations, which prove that a rotating sphere in an incompressibleviscous fluid near a wall (or free surface) can move in a translationaldirection orthogonal to the angular rate and parallel to the wall (orfree surface). See. e.g., J. Happel and H. Brenner, Low Reynolds NumberHydrodynamics: with special applications to particulate media, Springer1983, which is incorporated herein by reference. In FIG. 29b , whichrepresents movement on top of a surface, when the RWA spins onedirection (clockwise as shown), the sphere spins in the oppositedirection (counter-clockwise as shown), propelling the sphere to theleft.

A plurality of spherical robots can work in cooperation to facilitatelocomotion and overcoming various obstacles. As illustrated in FIG. 29c, a sequence of steps is shown for stacking a number of spherical robotsto increase the height of one or more robots, thus giving the uppermostrobot(s) an increased perspective to for collection of visualinformation or for other tasks that may require an obstacle to beovercome. In step 1, three spherical robots, designated as A, B and C,start off positioned side-by-side on a support surface. Robots A and Cmove toward robot B to squeeze B upward in step 2. In step 3, A and Ccome together with B balanced on top. In step 4, robots D and E areadded to the mix, with C and E being moved toward each other to squeezeD upward. A will move along with C to keep B on top. In step 5, B and Dare on top after C and E come together. Added spherical robots F and Gcombine with E in step 6 to force F upward, after which B, D and F aresupported on top of A, C, E and G. In step 7, B and F move toward eachother to squeeze D upward. In step 8, D moves up and to the right toclimb up on F while B moves back to the left. In step 9, the dynamicbalancing ability provided by the multiple momentum exchange elements ofeach robot allows D to balance on top of F which in turn balances on topof E, as shown in step 9. Stacking the spherical robots makes itpossible to position a robot with a camera or other sensor to look overan obstacle. Thus, the spherical robot, while taking advantage of a lowprofile to approach a target by passing under a variety of obstacles, astill able to cooperate with other similar robots to enable climbing toovercome obstacles.

In an exemplary application, multiple spherical robots can be deployed,with each robot carrying a different instrument or payload. The deployedrobots can cooperate to enable the robot carrying a particularinstrument to position itself optimally for completing its task. Inmilitary or law enforcement applications, the above-described sphericalrobot can be used in covert reconnaissance or munitions delivery.Commercial applications of the robot include incorporate of the robot atoy or a therapeutic device.

Fourth Multimodal Robot Embodiment

FIGS. 30-36 illustrate a fourth embodiment of the multimodal robot,which is a wirelessly-controlled vehicle that can perform the tasks ofobject retrieval, storage and throwing. The design includes anintegrated ball pick up mechanism and a throwing arm. Although describedin the example as a ball-handling robot, the fourth embodiment is notlimited to balls, but may be adapted to pick up and throw other objectsthat are sufficiently symmetric to allow the pick-up mechanism to work.Similarly, the throwing arm, described in the example as “jaialai-style”, is not limited to a jai alai shape, but may be of differentshapes depending on the desired speed, trajectory and spin of the objectbeing thrown.

To enable ball pick up, the body and wheels of the robot are spaced toprovide automatic pickup and loading of the target balls. This featureallows the operator to drive the robot toward the target, with thecurvature of the robot directing the ball into the space between thewheel and the body. The rotation of the wheel brings the ball up to bestored within a basket or other storage receptacle.

For throwing, the robot is stabilized by a feedback control circuit tobalance upright as an inverted pendulum. The rotational inertia producedby the motors that drive the wheels allows the robot to rotate the bodyrapidly from a lay-down mode to an upright mode. This rapid rotationresults in the effective toss of a lightweight ball. The exemplary shapeof the throwing arm imparts a spin to the ball as it rolls off thethrowing arm track, resulting in a more stable and longer throw.

As illustrated in FIGS. 30 and 31, the fourth robot embodiment 300includes a molded body 302 that is roughly cylindrical in shape(circular as viewed from the side) with a diameter and a width (betweenthe wheels) that is approximately three times the diameter of the targetobject. In the exemplary embodiment, the target object is a ping pongball with a diameter of about 40 mm. Two coaxial wheels 306 are mountedon a rotational axis 303. Each wheel 306 is independently driven by amotor (not shown) that is responsive to active feedback controls toprovide the robot with a self- balancing function. Control electronicsfor receiving feedback and actuating the motors are mounted on a printedcircuit board (not shown) that is housed under a removable back cover309. One or more batteries (not shown) for providing power to the motorsand electronics are preferably enclosed within the lower portion of body302, below the rotational axis 303, and are also accessible through backcover 303. The center of gravity of the robot is above the rotationalaxis so that when the motors are disconnected from its power source,i.e., switched off, the robot falls over.

The vertical arm 304 is configured as a track for launching the objectas well as being a mass the enables backward and forward motions throughleaning. In the exemplary embodiment, the track has a slight curvaturethat is similar in design to a jai alai cesta (basket). When the robotleans forward, it moves forward to restore vertical balancing. Turningis facilitated by rotating the wheels in opposite directions.

The feedback controls that enable self-balancing rely on a comparison ofthe signals of two MEMS (micro electro-mechanical systems)accelerometers, which are well known in the art. One such accelerometer324 is located on a platform 322 near the upper end 318 of the verticalarm 304. The feedback from this sensor may be turned off or ignored toallow a horizontal orientation of the robot with the arm 304 (actually,the bottom surface of platform 322) dragging on the support surface, asshown in FIG. 36a . Orientation in the horizontal mode is necessary toinitiate the throwing process. The second accelerometer is locatedcoplanar with, and at a fixed distance from, the first. In the exemplaryembodiment, the second accelerometer is located on the printed circuitboard under removable back cover 309, near the axis of rotation 303 ofthe wheels 306. Comparing the signals from the two accelerometers yieldsdecoupled rotational and translational acceleration measurements.

Referring to FIGS. 31a and b, the pick-up mechanism comprises a circularchannel 312 formed on each side of a central plane bisecting the robotbetween the lower portion of body 302 and the inner surface of the wheel306. The body has a peaked leading edge 310 that is coincident with thecentral plane. The leading edge 310 acts as a guide, similar to the bowof a ship, to direct the target object (ball) to one side of thecenterline and toward one of the channels 312. The scooped contour ofthe hub sections 308, in combination with the inner surface of thewheels and the guide 310, define channels 312, which direct the ballinto position for pick-up. The inner surface of each wheel has acompressible foam insert 307 to generate friction against the ball,causing it to be captured within the channel to be drawn along with thewheel as it rotates. Other methods for generating sufficient friction tocapture the ball between the hub and the inner surface of the wheel maybe used, including spring-loaded tracks, other compressible/resilientsurfaces, or rough textures molded into or applied to the inner surfacesof the wheels to generate sufficient friction to pull the ball into thechannel.

Referring to FIGS. 32a and 32b , as the wheel 306 rotates forwardrelative to the body, the ball rolls within the channel 312 into astorage volume 316 located at the center of a hollow portion of body302, between hubs 308. (For clarity, the body is shown with the wheelremoved.) Since the robot is able to turn on a point due to theindependent operation of the wheels, similar to a treaded vehicle, ballpickup is possible even when the robot spins in place, as long as thewheel in contact with the ball is moving forward with respect to thebody 302 to draw the ball into the channel.

Referring again to FIGS. 31a and 31b , in the upper portion of body 302,channels 312 continue into a curved passageway defined by channel covers314, which help guide the ball into the storage volume 316 within thebody 302. At the opening defined by the edge of each channel cover 314is a spring-loaded flipper 330. A detailed view of the flipper 330 canbe seen in FIG. 33. The flipper 330 is depressed by the ball as itenters the channel cover 314 and approaches the storage volume, thenresiles once the ball is past to extend up into the channel 312 toprevent the ball from leaving the storage volume through the channel.Once the ball is in the storage volume 316, it is ready to be thrown.

The ball release mechanism 340, illustrated in FIGS. 34a and 34b , ismounted within the center of body 302 within the storage volume 316.(The location of mechanism 340 can be seen in FIGS. 35a-35c .) The ballrelease mechanism consists of a gate 342 which is connected to a servomotor 344 by a push rod 346 and a cylindrical sliding collar 347. Thepush rod 346 slides freely along the axis of the cylindrical slidingcollar 347 and is displaced in the direction normal to the cylindricalsliding collar. The servo motor 344 may be radio-controlled or activatedby a system controller (not shown). The gate 342 has a curved surfacethat is shaped to match the exterior dimensions or the ball. The arclength and/or angle of the gate is preferably large enough to preventpassage of multiple balls while being small enough to minimize servomovement and release time.

FIGS. 35a-35c are cross-sectional views of the robot body illustrating asequence of steps within the ball release function. In FIG. 35a , therobot 300 is in an upright orientation, which is the appropriateorientation for collecting the balls for storage within the storagevolume 316. The ball release mechanism 340 is in its normally closedposition to prevent balls from escaping from the storage volumeunintentionally. The shape of the gate 342 allows a single ball to sitat the base 348 of the throwing arm 304 while the robot is upright. Thebottom of storage volume 316 is sloped toward the rear of the body toencourage the ball toward the throwing arm base 348.

FIG. 35b shows the robot after rotation of the body and throwing arm toa horizontal orientation. The gate 342 of ball release mechanism 340remains closed to prevent balls 320 from rolling out of the storagevolume.

In FIG. 35c , when the throwing function is to be executed, the servomotor 344 of ball release mechanism 340 is triggered to open the gatebriefly to allow one ball 320 onto the track of throwing arm 304.

FIGS. 36a-36d illustrate a sequence of steps of the throwing orlaunching function. By conservation of angular momentum around therobot's center of gravity, the throw can be performed by rapid reverseacceleration of the wheels 306 in a direction away from the throwingarm. This causes the body 302 to suddenly rotate in the oppositedirection, so that the throwing arm 304 quickly rotates up and forward.As seen in FIGS. 36b -36 d, the throwing motion imparts a forwardvelocity on the ball relative to the support surface. Because the ballrolls along the track rather than sliding up to the release end 318, thetrack imparts a backspin on the ball 320, which improves flightstability and effective range. The fourth embodiment of the multimodalrobot may be controlled remotely by wireless communication with a simplejoystick and/or push button controller, or it may possess sensors(optical, audio, temperature, chemical, etc.) and internal circuitryincluding a computer controller capable of effecting autonomous behaviorwith adaptive response to the sensor feedback of environmentalconditions. Using vision, motion, heat or other object detectiontechnology, the robot may be capable of tracking and seeking a targetobject to pick up, store and throw to a user or another robot. Anotherpotential embodiment may consist of just object pick up and storage forthe purpose of object retrieval and transport. Adaptive behavior would,for example, allow the robot to be operated in horizontal mode to passunder obstacles or to maintain a low profile to avoid detection,shifting to the vertical orientation as needed to pick up an object andreturn to horizontal mode to initiate a launching sequence.Additionally, the robot may be configured for catching as well by meansof a modified track. The appeal of a catching robot is the activeresponsiveness of the robot's self-balancing. The combined abilities ofthe fourth multimodal robot embodiment to catch, throw, seek and pick upobjects autonomously would allow for “team” sports or roboticscompetitions.

The above-described multimodal robots all incorporate a number of designfeatures that are important to their successful operation. Thesefeatures include (1) multifunctional wheels, which are used formain-drive, differential-steering wheels, upright actuators, reactionwheels, counterweights and ball pick-up mechanisms; (2) multifunctionalmotors used to produce completely different effects when drivenclockwise or counterclockwise by virtue or creative use of latchingmechanisms; (3) sensors that provide feedback to a system controller forreactive actuation of motors for balancing and locomotion; and (4)custom printed circuit boards used to connect exactly the rightelectronics together with a minimum footprint and mass, in addition tohigh-performance COTS boards such as the Texas Instruments C2000 MCU(used in the first embodiment), the National Instruments sbRIO 9602(used in the second embodiment) and the Technologic Systems TS-7250(used in the third embodiment), with both low-level coding in C as wellas high-level control design leveraging MathWork's MATLAB® SIMULINK®software and National Instrument's LabVIEW™ CD&Sim™ modules,respectively, to program the Texas Instruments and National Instrumentsboards.

The above-described robots by may be combined to perform a variety ofdifferent tasks that may be useful in areas including defense,counterterrorism, surveillance and law enforcement, industrialapplications, such as transport of payloads and environmental monitoringin areas that are hazardous or otherwise difficult to access, spaceexploration, entertainment, along with many other possible uses. Forexample, features of the tracked robot of the second embodiment could becombined with the throwing function of the fourth embodiment to allow arobot to travel over rough terrain and/or climb over obstacles, thedeliver an object by launching it using the throwing functions of thefourth embodiment.

While the foregoing written description contains many specifics, theseshould not be construed as limitations on the scope of the invention orof what may be claimed, but rather as descriptions of features specificto particular embodiments of the invention. Certain features that aredescribed in this specification in the context of separate embodimentscan also be implemented in combination in a single embodiment.Conversely, various features that are described in the context of asingle embodiment can also be implemented in multiple embodimentsseparately or in any suitable sub-combination. Moreover, althoughfeatures may be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination can in some cases be excised from the combination, and theclaimed combination may be directed to a sub-combination or variation ofa sub-combination.

1. A robotic system comprising: a body having a body length, a firstbody end, and a second body end; a pair of treaded arms disposed onopposite sides of the body each treaded arm comprising: a first arm endrotatably disposed on an axle defining a pivot point near the first bodyend, the first arm end having a first wheel rotatably disposed thereon;a second arm end having a second wheel rotatably disposed thereon,wherein the treaded arm has an arm length from the pivot point to thesecond arm end that is slightly longer than the body length from thepivot point to the second body end; and a tread having an inner surfaceconfigured to engage the first wheel and the second wheel, and an outersurface configured to contact a support surface; wherein each treadedarm is configured for rotation around the pivot point at a plurality ofarm angles relative to the body and to extend the second arm end awayfrom the body; a first motor associated with each treaded arm, the firstmotor configured to drive the tread around the associated treaded arm;at least one second motor associated with the treaded arms; a linkagebetween the at least one second motor and the axle for each treaded arm,wherein activation of the at least one second motor rotates one of thebody and the corresponding treaded arm relative to the other; a systemcontroller configured for generating a signal for actuating each motor;one or more sensors in communication with the system controllerconfigured for generating feedback signals to reactively actuate one ormore of the motors to control each treaded arm to dynamically shift acombined center of gravity of the body and treaded arms in line with acontact point on the support surface and to execute one or morefunctions selected from the group consisting of forward motion, backwardmotion, climbing, and balancing relative to the contact point; and apower source.
 2. The robotic system of claim 1, wherein the linkagebetween the at least one second motor and the axle for each treaded armand a linkage between the first motor and the first wheel areincorporated in a two-degree of freedom joint.
 3. The robotic system ofclaim 1, wherein the treaded arms are configured to rotateanti-symmetrically to extend an effective length of the robot.
 4. Therobotic system of claim 1, wherein the first wheels and the secondwheels each comprise sprockets configured to engage with the innersurface of the tread.
 5. The robotic system of claim 1, furthercomprising a plurality of wheels disposed on the second body end.
 6. Therobotic system of claim 1, wherein the system controller is configuredto generate signals to the at least one second motors to extend the bodyupward from the treaded arms and to the first motors to cause thetreaded arms to toe balance on the second arm ends.
 7. The roboticsystem of claim 1, wherein the system controller is configured togenerate signals to the at least one second motors to extend the bodyupward from the treaded arms and to the first motors to drive the treadsaround the treaded arms to effect forward motion or backward motion. 8.The robotic system of claim 1, wherein the system controller isconfigured to generate signals to the first motor and the at least onesecond motor to cause the body to extend upward from the treaded armswhile balancing on the second arm ends and to effect forward motion orbackward motion.
 9. The robotic system of claim 1, wherein the systemcontroller is responsive to a wireless remote control signal.
 10. Arobotic system, comprising: a body comprising a chassis, wherein thechassis is disposed near a first end of the body; a drive arm disposedon each side of the chassis at a pivot point, each drive arm having afirst arm end having a first wheel, and a second arm end having a secondwheel, wherein each drive arm is configured for rotation at the pivotpoint to effect a plurality of arm angles relative to the body and toextend the second arm end away from the body, and wherein an arm lengthfrom the pivot point to the second arm end is slightly longer than abody length from the pivot point to the second body end; a treadextending around each drive arm, the tread having an inner surfaceconfigured to engage the first wheel and the second wheel, and an outersurface configured to contact a support surface; a drive motorconfigured for rotating the tread around the drive arm; at least one armmotor configured for driving rotation of the drive arms and the chassisrelative to the other; a system controller configured for generating asignal for actuating each motor; one or more sensors in communicationwith the system controller configured for generating feedback signals toreactively actuate one or more of the motors to control each drive armto dynamically shift a combined center of gravity of the body and drivearms in line with a contact point on the support surface and to executeone or more functions selected from the group consisting of forwardmotion, backward motion, climbing, balancing relative to the contactpoint; and a power source.
 11. The robotic system of claim 10, furthercomprising a plurality of wheels disposed on a second end of the body.12. The robotic system of claim 10, further comprising a first linkagebetween the drive motor and the first wheel, and a second linkagebetween the at least one arm motor and an axle for each drive arm. 13.The robotic system of claim 12, wherein the first linkage and the secondlinkage are incorporated into a two-degree of freedom joint.
 14. Therobotic system of claim 10, wherein the first wheels and the secondwheels each comprise sprockets configured to engage with the innersurface of the tread.
 15. The robotic system of claim 10, wherein thesystem controller is configured to generate signals to the at least onearm motor to extend the body upward from the drive arms and to the drivemotors to cause the drive arms to toe balance on the second arm ends.16. The robotic system of claim 10, wherein the system controller isconfigured to generate signals to the at least one arm motor to extendthe body upward from the drive arms and to the drive motors to drive thetreads around the drive arms to effect forward motion or backwardmotion.
 17. The robotic system of claim 10, wherein the systemcontroller is configured to generate signals to the drive motor and atleast one arm motor to cause the body to extend upward from the drivearms while balancing on the second arm ends and to effect forward motionor backward motion.
 18. The robotic system of claim 10, wherein thesystem controller is responsive to a wireless remote control signal. 19.A method for maneuvering a robotic system having a body comprising achassis and a pair of treaded drive arms disposed on opposite sides ofthe chassis near a first body end, wherein each treaded drive arm has afirst arm end having a first wheel, a second arm end having a secondwheel, and a tread extending around the first wheel and the secondwheel, the first wheel being rotatably disposed on an axle coaxial withthe chassis at a pivot point, wherein an arm length from the pivot pointto the second arm end is slightly longer than a body length from thepivot point to the second body end, and wherein each drive arm isconfigured for rotation at different arm angles relative to the body andto extend the second wheel away from the body, the method comprising:providing a drive motor for rotating the tread of each treaded drivearm; providing at least one arm motor for rotating the chassis and thetreaded drive arms relative to each other; activating the at least onearm motor to rotate the chassis at a non-parallel angle relative to asupport surface; activating the drive motors to lift one of the firstwheel and the second wheel away from the support surface so that thetread associated with the other wheel is in contact with a contact pointon the support surface; activating the at least one arm motor toposition the chassis at a balance angle relative to the treaded drivearms to shift a combined center of gravity of the body and treaded drivearms over the contact point; and activating the drive motors to maintainthe combined center of gravity over the contact point.
 20. The method ofclaim 10, wherein the balance angle defines a C-balancing mode, whereinthe first wheel is lifted and the second wheel corresponds to thecontact point.